setgroups() problem w/ arla module loaded

[Harald Barth]

> Nice work on the latest arla!  It seems to work properly under SuSE 9.1 
> with the 2.6.4 kernel.

Almost, as you noticed, but more below.

> However, with /afs active (arlad and kernel module loaded), postfix is 
> going down with this in the system logs:
> 
> Jun 21 07:51:48 monarch postfix/master[5288]: fatal: setgroups(1, &0): Bad address
> 
> If I turn the service off, it runs fine.
> 
> Is this a known/expected issue?  Something to do with how you manage PAG 
> based credentials?

Right. We (*) noticed the problem directly when we finally tried to
build on SuSE 9.1. The nnpfs kernel module broke setgroups(). It _is_
a bug, but it hides quite well if you use the kernel.org kernels which
we used first. The differences between a x.y.z from kernel.org and a
x.y.z from SuSE and a x.y.z from Fedora2 can be quite significant.
After some really frustrating days (at least for me) we finally found
the bug and it resulted in the stuff you find here:

file:///afs/stacken.kth.se/ftp/pub/arla/distributions/SuSE-9.1/
          ftp://ftp.stacken.kth.se/arla/distributions/SuSE-9.1/

The bug fixes in the SRPM will be merged or are allready merged into
the main repository.

The arla-0.36-4 RPM has nnpfs kernel modules for the following
kernels:

kernel-default-2.6.4-52
kernel-bigsmp-2.6.4-54.5
kernel-default-2.6.4-54.3
kernel-default-2.6.4-29
kernel-smp-2.6.4-54.3
kernel-bigsmp-2.6.5-7.75
kernel-docs-2.6.4-52
kernel-default-2.6.4-54.5
kernel-syms-2.6.4-54.5
kernel-bigsmp-2.6.4-54.3
kernel-default-2.6.4-34
kernel-smp-2.6.4-34
kernel-default-2.6.5-7.75
kernel-syms-2.6.5-7.75
kernel-syms-2.6.4-52
kernel-smp-2.6.4-54.5
kernel-bigsmp-2.6.4-34
kernel-syms-2.6.4-54.3
kernel-smp-2.6.5-7.75

If you use another kernel (all days are "new-kernel" days), you need a
build environment and to use the SRPM. 

Known issues:

      * You need an ext[23] partition mounted at /var/cache/arla
      
      Reiserfs has mangled my cache serveral times :-( As ext2 is
      faster than ext3 and there is no valuable data in there,
      I use mostly ext2. There are checks in /etc/init.d/arla 
      to prevent you doing different. If you know what you are
      doing, you can modify the script :-)

      * The locations of the installed files from the RPM are
      more Linux-ish compared to "make install" from the source.

      * On SMP, there might still be some lock issues lurking,
      sometimes processes hang. But that can be solved by
      interrupting the hanging process with Control-C. Tell
      us if you have these or even know how to reproduce.

We havn't hade any chance to test this stuff for a longer time, so
surprises might still be lurking. It hasn't blown up my files, but
that is no guarantee that it won't blow up in your face. Backup is a
good.

Harald.

(*) "we" as in Tomas, Jimmy, Alexander and myself.